Depth Of Field can be hard to understand. Two main aspects of depth of field are, Aperture and Focus Points.
Aperture - A large f-number such as f/32, (which means a smaller aperture) will bring all foreground and background objects in focus, while a small f-number such as f/1.4 will isolate the foreground from the background by making the foreground objects sharp and the background blurry.
Focus Points - Its basically where you set the main focus, normally its set to the middle, but it can be moved around.
Aperture - A large f-number such as f/32, (which means a smaller aperture) will bring all foreground and background objects in focus, while a small f-number such as f/1.4 will isolate the foreground from the background by making the foreground objects sharp and the background blurry.
Focus Points - Its basically where you set the main focus, normally its set to the middle, but it can be moved around.